New Delhi, Aug. 10 -- NAGASAKI - Eighty-one years after an American B-29 dropped a plutonium bomb on this city and killed as many as 80,000 people, Japan's prime minister stood at the annual memorial ceremony and spoke of "the disasters that occurred 81 years ago" without once naming who caused them.

Sanae Takaichi, speaking Saturday at Nagasaki's Peace Park, invoked Japan's three non-nuclear principles and pledged that the country would "continue realistic and practical efforts to achieve a world without nuclear weapons." She mentioned Hiroshima and Nagasaki by name. She did not mention the United States.

The omission drew a sharp public response from Moscow. Maria Zakharova, spokeswoman for the Russian Foreign Ministry, mocked Japan's...